Development of new treatment strategy by dendritic cells for combination therapy against gastrointestinal cancers

为了探索树突状细胞治疗胃肠道肿瘤的新策略，本研究采用基因芯片和代表性差异分析技术，检测了食管癌细胞系和正常食管上皮细胞系基因和蛋白表达的差异。在已鉴定的基因（拉格-1、MAGE-A1、cyclin D2等）中，我们发现cyclin D2在食管癌组织中的表达低于正常上皮。利用甲基化特异性PCR、HDAC抑制剂和去甲基化试剂，我们证明了cyclin D2基因启动子区的转录抑制和沉默。与肿瘤特异性抗原的表观遗传控制有关，化疗还表现为诱导肿瘤特异性基因和抗肿瘤免疫。我们已经报道了凋亡肿瘤细胞和树突状细胞之间的相互作用可能与化疗诱导抗肿瘤免疫的机制有关。从这个角度来看，我们研究了TRAIL（由活化的树突状细胞产生）与化疗联合的凋亡机制。化疗使肿瘤细胞死亡受体增加，而使正常淋巴细胞诱骗受体增加。这些结果表明化疗后局部树突状细胞的聚集对正常细胞的保护作用和肿瘤细胞的凋亡作用。化疗和树突状细胞的联合治疗将打破肿瘤的表观遗传沉默，诱导肿瘤消退和特异性抗肿瘤免疫。

In order to develop new treatment strategy against gastrointestinal cancers using dendritic cells, we examined the expressional differences of genes and proteins between esophageal cancer cell lines and normal epithelial cell lines from the esophagus with microarray and representational difference analysis. In identified genes (LAGE-1, MAGE-A1, cyclin D2, etc), we revealed the low expression profile of cyclin D2 in esophageal cancer tissues, compared with normal epithelia. Using methylation-specific PCR, HDAC inhibitor, and demethylation agent, we demonstrated the transcriptional repression and silence of promoter region of cyclin D2 gene. In relation with epigenetic control of tumor specific antigen, chemotherapy also showed induction of tumor specific genes and antitumor immunity. We have reported interaction between apoptotic tumor cells and dendritic cells might relate induction mechanisms of antitumor immunity by chemotherapy. From this point of view, we examined the apoptotic mechanisms of TRAIL (produced by activated dendritic cells) in combination with chemotherapy. Chemotherapy increased death receptor on tumor cells, but increased decoy receptor on normal lymphoid cells. These results showed the protection of normal cells and apoptosis of tumor cells in local accumulation of dendritic cells after chemotherapy. Combination therapy with chemotherapy and dendritic cells will break epigenetic silence of tumors and induce tumor regression and specific antitumor immunity.